Mitigated-Force Carriage for High Magnetic Field Environments

ABSTRACT

A carriage for high magnetic field environments includes a plurality of work-piece separators disposed in an operable relationship with a work-piece processing magnet having a magnetic field strength of at least 1 Tesla for supporting and separating a plurality of work-pieces by a preselected, essentially equal spacing, so that, as a first work-piece is inserted into the magnetic field, a second work-piece is simultaneously withdrawn from the magnetic field, so that an attractive magnetic force imparted on the first work-piece offsets a resistive magnetic force imparted on the second work-piece.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 13/329,373, filed on Dec. 19, 2011, which is incorporatedherein in its entirety by reference. This application also claimspriority to U.S. Provisional Application No. 61/543,984, filed on Oct.6, 2011, which is incorporated herein in its entirety by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

The United States Government has rights in this invention pursuant tocontract no. DE-AC05-000R22725 between the United States Department ofEnergy and UT-Battelle, LLC.

BACKGROUND OF THE INVENTION

High magnetic field processing of materials is of great interest,especially in the processing of certain alloys, to achieve superiorproperties and characteristics. Work-pieces of materials are passed inand out of high magnetic fields to affect the properties andcharacteristics of the processed materials. Such processes andassociated apparatus are well known; see for example; U.S. Pat. No.7,745,765 issued on Jun. 29, 2010 to Ludtka, et al. entitled “Thermaland High Magnetic Field Treatment of Materials and AssociatedApparatus”; U.S. Pat. No. 7,161,124 issued on Jan. 9, 2007 to Kisner, etal. entitled “Thermal and High Magnetic Field Treatment of Materials andAssociated Apparatus”; and U.S. Pat. No. 6,773,513 issued on Aug. 10,2004 to Kisner, et al. entitled “Method for Residual Stress Relief andRetained Austenite Destabilization”.

A high magnetic field environment generally comprises a uniform maximummagnetic field region surrounded by a gradient magnetic field region.When a ferromagnetic material is either inserted into or removed from ahigh magnetic field region, the magnetic field gradient region imparts asignificant force which must be overcome in order to move the materialinto or out of position. For example, low carbon steel in a 9 Teslasuperconducting magnet with a gradient scale length of ⅙ meter isgenerally subject to an attractive magnetic force of 280 lbs. per cubicinch of steel. Therefore, to insert and/or remove a relatively largework-piece into a high magnetic field region such as a thermomagneticprocessing device, the work-piece can experience forces on the order ofhundreds to thousands of pounds. Such resistive force makes work-pieceinsertion and/or removal a potentially difficult task.

The high resistive force issue is a negative driving force for carriage(work-piece handling and/or transport system) design that requires verylarge and cumbersome framework to overcome the high forces that areimparted upon the work-piece during insertion and removal processes. Itis desirable to mitigate such resistive forces in a magnetic fieldenvironment to facilitate ease of work-piece loading, in many cases formagnets having as little as 1 Tesla.

BRIEF SUMMARY OF THE INVENTION

In accordance with some examples of the present invention, a carriagefor high magnetic field environments that includes a first work-pieceholding means for holding a first work-piece, the first work-pieceholding means being disposed in an operable relationship with awork-piece processing magnet having a magnetic field strength of atleast 1 Tesla. The first work-piece holding means is further disposed inoperable connection with a second work-piece holding means for holding asecond work-piece so that, as the first work-piece is inserted into themagnetic field, the second work-piece is simultaneously withdrawn fromthe magnetic field, so that an attractive magnetic force imparted on thefirst work-piece offsets a resistive magnetic force imparted on thesecond work-piece.

In accordance with other examples of the present invention, a dual stagecarriage for high magnetic field environments includes a primarytraversing frame disposed in an operable relationship with a work-pieceprocessing magnet having a magnetic field strength of at least 1 Tesla,the primary traversing frame further disposed in operable connectionwith a first work-piece holding means for holding a first work-piece;and a secondary traversing frame supported by the primary traversingframe and disposed in operable connection to a second work-piece holdingmeans for holding a second work-piece. With the second work-piece in themagnetic field, the first work-piece can be moved from a positionessentially outside effective bounds of the magnetic field toward thesecond work-piece to a preselected spacing from the second work-piece,then, as the first work-piece holding means is inserted into themagnetic field, the second work-piece holding means is simultaneouslywithdrawn from the magnetic field, so that an attractive magnetic forceimparted on the first work-piece offsets a resistive magnetic forceimparted on the second work-piece, and then, with the first work-piecebeing within the magnetic field, the second work-piece can be moved fromthe preselected spacing from the first work-piece away from the firstwork-piece to a position essentially outside the effective bounds of themagnetic field.

In accordance with other examples of the present invention, a carriagefor high magnetic field environments includes a plurality of work-pieceseparators disposed in an operable relationship with a work-pieceprocessing magnet having a magnetic field strength of at least 1 Teslafor supporting and separating a plurality of work-pieces by apreselected, essentially equal spacing. As a first work-piece isinserted into the magnetic field, a second work-piece is simultaneouslywithdrawn from the magnetic field, so that an attractive magnetic forceimparted on the first work-piece offsets a resistive magnetic forceimparted on the second work-piece.

In accordance with other examples of the present invention, a carriagefor high magnetic field environments includes a continuous, looped,flexible, work-piece holding conveyor disposed in an operablerelationship with a work-piece processing magnet having a magnetic fieldstrength of at least 1 Tesla, the conveyor defining a plurality ofessentially equally spaced work-piece holding positions. As the conveyormoves a first work-piece into the magnetic field, the conveyor alsosimultaneously withdraws a second work-piece from the magnetic field, sothat an attractive magnetic force imparted on the first work-pieceoffsets a resistive magnetic force imparted on the second work-piece.

In accordance with further examples of the present invention, a methodof moving work-pieces into and out of a high magnetic field environmentincludes the steps of: providing a first work-piece holding means thatis holding a first work-piece and a second work-piece holding means thatis holding a second work-piece, the first work-piece holding means beingdisposed in operable connection with the second work-piece holdingmeans; with the first work-piece holding means, holding the firstwork-piece disposed without a magnetic field having strength of at least1 Tesla while, with second work-piece holding means, holding the secondwork-piece disposed within the magnetic field; and moving the firstwork-piece holding means and the second work-piece holding means tosimultaneously insert the first work-piece into the magnetic field andwithdraw the second work-piece from the magnetic field, so that anattractive magnetic force imparted on the first work-piece offsets aresistive magnetic force imparted on the second work-piece.

In accordance with still further examples of the present invention, amethod of moving work-pieces into and out of a high magnetic fieldenvironment includes the steps of: providing a primary traversing framedisposed in an operable relationship with a work-piece processing magnethaving a magnetic field strength of at least 1 Tesla, the primarytraversing frame further disposed in operable connection with a firstwork-piece holding means that is holding a first work-piece, and asecondary traversing frame supported by the primary traversing frame anddisposed in operable connection to a second work-piece holding meansthat is holding a second work-piece; with the second work-piece in themagnetic field, moving the first work-piece from a position essentiallyoutside effective bounds of the magnetic field toward the secondwork-piece to a preselected spacing from the second work-piece; as thefirst work-piece is inserted into the magnetic field, simultaneouslywithdrawing the second work-piece from the magnetic field whilemaintaining the preselected spacing, so that an attractive magneticforce imparted on the first work-piece offsets a resistive magneticforce imparted on the second work-piece; and with the first work-piecebeing within the magnetic field, moving the second work-piece from thepreselected spacing from the first work-piece away from the firstwork-piece to a position essentially outside the effective bounds of themagnetic field.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a single stage carriage in a firstposition in accordance with an example of the present invention.

FIG. 2 is a schematic diagram of a single stage carriage in a secondposition in accordance with an example of the present invention.

FIG. 3 is a schematic diagram of a single stage carriage in a thirdposition in accordance with an example of the present invention.

FIG. 4 is a schematic diagram of a dual stage carriage in a firstposition in accordance with an example of the present invention.

FIG. 5 is a schematic diagram of a dual stage carriage in a secondposition in accordance with an example of the present invention.

FIG. 6 is a schematic diagram of a dual stage carriage in a thirdposition in accordance with an example of the present invention.

FIG. 7 is a schematic diagram of a dual stage carriage in a fourthposition in accordance with an example of the present invention.

FIG. 8 is a schematic diagram of a carriage configured for continuousstraight-line processing in accordance with an example of the presentinvention.

FIG. 9 is a schematic diagram of a carriage configured for continuousloop processing in accordance with an example of the present invention.

FIG. 10 is a schematic diagram of a carriage configured forhydraulically actuated reciprocal movement of work-pieces through amagnetic field in accordance with an example of the present invention.

FIG. 11 is a graph showing net extraction force on a pair oftransmission shafts, with various spacing in accordance with examples ofthe present invention, compared with the extraction force on a singletransmission shaft.

FIG. 12 is a graph showing net extraction force on a set of fouruniformly spaced transmission shafts in accordance with examples of thepresent invention, compared with the extraction force on a singletransmission shaft.

For a better understanding of the present invention, together with otherand further objects, advantages and capabilities thereof, reference ismade to the following disclosure and appended claims in connection withthe above-described drawings.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a work-piece handling system (hereinaftercalled a carriage) that is disposed in an operable relationship with awork-piece processing magnet having a magnetic field strength of atleast 1 Tesla. The carriage is preferably made of nonmagnetic materialand/or is of sufficiently strong construction to not be bent, warped, orotherwise misshapen by the magnetic field. The carriage holds andsimultaneously moves both the work-piece and a counter-work-piece in andout of a magnetic field gradient region. The counter-work-piece issubjected to a generally opposing and optimally equal force due to themagnetic field gradient region where the work-piece is located. Thus,the forces are essentially opposite and therefore at least partiallycancel each other out. Work-piece handling equipment can besignificantly smaller than conventional equipment because it will nothave to be designed to handle extremely high loads as is currentlyrequired.

The counter-work-piece can be a second work-piece, or it can be a dummywork-piece. The work-piece and the counter-work-piece should beidentical, or at least as similar as possible in order to ensure theclosest possible match in the counter directed magnetic forces. Thework-piece and the counter-work-piece must be disposed in an operablemechanical connection so that they move simultaneously within thegradient magnetic field while essentially maintaining a preselectedspacing therebetween.

An example of a single stage carriage in accordance with the presentinvention is shown in FIGS. 1-3. A carriage 10 is representedschematically and a magnetic field 12 is represented by a diagram ofmagnetic field gradient lines, the innermost representing the strongestregion of the magnetic field 12. The magnetic field 12 represents awork-piece processing magnet having a field strength of at least 1Tesla.

The carriage 10 comprises a traversing frame 14, a work-piece holder 16,and a counter-work-piece holder 18. A work-piece 20 and acounter-work-piece 22 are held at a preselected spacing 21 and can beinterchangeable. As illustrated, the traversing frame 14 can be disposedessentially outside the effective bounds of the magnetic field 12.

As described hereinabove, the carriage 10 is preferably of sufficientlystrong construction to remain essentially rigid when moving work-pieces20, 22 in and out of the magnetic field 12. The carriage 10 ispreferably made of nonmagnetic material. The work-piece holder 16 andthe counter-work-piece holder 18 are also interchangeable, preferablynonmagnetic, and can comprise any conventional means for holding awork-piece for insertion into a processing apparatus such as a magnet.Suggested work-piece holding means can include at least one of, (but notlimited to) a threaded link, a bolt, a stud, a friction grip, a collet,a chuck, a hook, a latch, a locking pin, a clasp, a snap, a spring, aclamp, a fastener, a wedge, and the like.

In operation, the carriage 10 moves (traverses) in the direction of thearrows 24, 26 from a first position as shown in FIG. 1, through a secondposition as shown in FIG. 2, and into a third position as shown in FIG.3. As the work-piece 20 is moved out of the magnetic field 12, thecounter-work-piece 22 is simultaneously moved into magnetic field 12 formagnetic processing. During the moving process, attractive magneticforce imparted on the counter-work-piece 22 at least partially offsets aresistive magnetic force imparted on the work-piece 20. Ideally, theattractive magnetic force imparted on the counter-work-piece 22completely offsets the resistive magnetic force imparted on thework-piece 20, resulting, ideally, in an essentially zero-forcemovement. Thus, the counter-work-piece 22 assists in the removal of thework-piece 20.

Spacing 21 of the work-pieces 20, 22 is important in carrying out thepresent invention for optimizing the force offset and thus minimizingthe force necessary. Spacing 21 can be adjustable to accommodate varioussizes of work-pieces 20, 22. Work-piece holders 16, 18 can be ofadjustable length, or can be interchangeable with other work-pieceholders (not shown) of different lengths.

The work-piece 20 can be exchanged with a new work-piece when thecarriage 10 is in the position shown in FIG. 3. Subsequently thecarriage 10 can be moved in the opposite direction, back to the positionshown in FIG. 1. The counter-work-piece 22 can be exchanged in thatposition.

FIGS. 4-7 show various operational positions of a dual stage carriage 30in accordance with another example of the present invention. A primarytraversing frame comprises a pair of anchored primary telescoping arms32 support a primary cross-member 34. The primary cross-member 34supports a secondary traversing frame comprising a pair of secondarytelescoping arms 36 that support a secondary cross-member 38. Theprimary cross-member 34 supports a counter-work-piece holder 40 andcounter-work-piece 42, and the secondary cross-member 38 supports awork-piece holder 44, and work-piece 46. As illustrated, all of thecomponents of the dual stage carriage 30 except the counter-work-pieceholder 40 and the work-piece holder 44 can be disposed essentiallyoutside the effective bounds of the magnetic field 12.

FIG. 4 shows the dual stage carriage 30 in a first operational positionwherein the counter-work-piece 42 is accessible and can be replaced ifdesired. The work-pieces 42, 46 are shown at an initial spacing 41. In afirst, compound movement, primary telescoping arms 32 partially retractwhile the secondary telescoping arms 36 fully retract to move primarycross-member 34 in the direction indicated by arrow 50 to the secondoperational position shown in FIG. 5. The secondary cross-member 38,work-piece holder 44, and work-piece 46 remain essentially stationaryduring the first movement. The purpose of the first movement is to movethe counter-work-piece 42, into a proximity of the magnetic field 12without moving the work-piece 46. The work-pieces 42, 46 are shown at asecond spacing 43.

In a second, simple movement, primary telescoping arms 32 fully retractto move primary cross-member 34 in the direction indicated by arrow 52in FIG. 5 to the third operational position shown in FIG. 6. Since thesecondary telescoping arms 36 are already fully retracted, the secondarycross-member 38, work-piece holder 44, and work-piece 46 aresimultaneously moved therewith, as indicated by arrow 54 in FIG. 5. Thework-pieces 42, 46 remain at the second spacing 43. The purpose of thesecond movement is to move the counter-work-piece 42 into the magneticfield 12 (optionally for magnetic processing) while simultaneouslymoving the work-piece 46 out of the magnetic field 12. Thecounter-work-piece 42 assists in removal of the work-piece 46 asdescribed hereinabove, offsetting magnetic forces.

In a third, simple movement, the secondary telescoping arms 36 fullyextend to move the secondary cross-member 38, work-piece holder 44, andwork-piece 46 in the direction indicated by arrow 56 in FIG. 6 to thefourth operational position shown in FIG. 7. The primary cross-member34, counter-work-piece holder 40, and counter work-piece 42 all remainessentially stationary during the third movement. The purpose of thethird movement is to move the work-piece 46, out of a proximity of themagnetic field 12 without moving the counter-work-piece 42. The spacingof work-pieces 42, 46 is restored to the initial spacing 41 shown inFIG. 4. In the fourth operational position the work-piece 46 isaccessible and can be replaced if desired.

The movements shown in FIGS. 4-7 can be subsequently repeated in reverseorder in order to return the dual stage carriage 30 to the firstoperational position shown in FIG. 4. Thus, a complete cycle isconsummated.

FIG. 8 shows an example of the present invention configured forcontinuous straight-line movement of work-pieces through a magneticfield 12, each work-piece acting as a counter-work-piece for thepreceding work-piece. In this general illustration, five identicalwork-pieces 150, 152, 154, 156, 158 are interconnected and supportedessentially equidistantly by work-piece separators 60, 62, 64, 66, 68,all of essentially equal, preselected length 74 in the fashion of achain 70. The work-piece separators 60, 62, 64, 66, 68 in this exampleare adapted to support a work-piece at each end thereof, separating thework-pieces by preselected, essentially equal spacing. The firstwork-piece 150 and the work-piece separator 60 comprise a segment of thechain 70, and so on. A chain can be comprised of as few as twowork-pieces and two work-piece separators, or as many as is suitable fora particular application.

Also shown in FIG. 8 is an optional arrangement wherein a work-piece 153is held by work-piece station 151. A work-piece station 151 can bedefined as any conventional structure operably connectable to awork-piece separator 60, 62, 64, 66, 68, and adapted for holding awork-piece 153 for processing. A work-piece 153 can be held in awork-piece station 151 by any of the work-piece holding means describedhereinabove.

In a unidirectional mode of operation, the chain 70 is moved only in thedirection of the arrow 72 the length of one segment. Work-piece 154 ismoved out of the magnetic field 12 with the assistance of work-piece152, which is simultaneously moved into the magnetic field 12 formagnetic processing. Magnetic forces are offset as describedhereinabove. Subsequently, the segment comprising last work-piece 158and the work-piece separator 68 can be removed and separated. Anotherwork-piece can be connected to the work-piece separator 68 and added tothe chain 70 above the first work-piece 150 as a new segment, and theabove steps are repeated.

Alternatively, the example of the present invention shown in FIG. 8 canbe operated in a bidirectional mode, moving the chain 70 alternately inthe direction of the arrow 72 and in the opposite direction. Processedwork-pieces can be removed and new work-pieces can be added at bothends, in alternating fashion.

FIG. 9 shows an example of the present invention configured forcontinuous loop processing. Work-pieces move in succession through amagnetic field 12, each work-piece acting as a counter-work-piece forthe preceding work-piece. In this general illustration, a continuous,looped, flexible, work-piece holding conveyor 80 may include at leastone of a belt and a chain. The 80 has a plurality of essentially equallyspaced (represented by dimension 81) work-piece holding positions 82,84, 86, 88, 90, 92, 94, 96, 98, 100, 102, 104, all holding a respectivework-piece except positions 102 and 104, which are shown as empty. Abelt can be configured to hold as few or as many work-pieces as issuitable for a particular application. Also shown are four wheels 106around which the conveyor 80 travels in circuitous fashion, undersufficient tension to maintain the preselected spacing 81. Any one orall of the wheels 106 may be powered for moving the conveyor 80. Thewheels 106 can be toothed or non-toothed, and can be any of, forexample, gears, cogs, pulleys, sprockets, and the like.

In operation, the conveyor 80 is moved in the direction of the arrows108 the length of one position. In accordance with an example thepresent invention, the work-piece at position 90 is moved out of themagnetic field 12 with the assistance of the next-in-line work-piece 88,which is simultaneously moved into the magnetic field 12 for magneticprocessing; the movement repeating as desired. Magnetic forces areoffset as taught hereinabove. With reference to respective arrows 110,112, new work-pieces are added to the conveyor 80 at position 82, whileprocessed work-pieces are removed at position 100. In other examples ofthe present invention, work-pieces can be removed and replaced with newwork-pieces at the same position.

Other processes may occur in sequence with magnetic processing.Pre-processing such as preheating, precooling, and/or analysis,represented by box 114, may occur at position 86. Post-processing suchas heating, cooling, and/or analysis, represented by box 116, may occurat position 94.

FIG. 10 shows an example of the present invention configured forhydraulically actuated reciprocal movement of work-pieces in and out ofa magnetic field 12 for magnetic processing. First and seconddouble-acting hydraulic cylinders 120, 122 (also called linear hydraulicmotors) have respective piston rods 124, 126 that are adapted to holdrespective counter-work-piece 128 and work-piece 130. A hydraulic pumpand control unit 127 has respective hydraulic lines 132, 134 torespective distal connections 136, 138 of the hydraulic cylinders 120,122. Respective proximal connections 140, 142, are connected to eachother by hydraulic equalization lines 144, 145, and an optionalhydraulic controller 147, which can be simple valve and reservoir systemthat can be used to hydraulically adjust and/or maintain the spacing 148of the work-pieces 128, 130.

In operation, the hydraulic pump and control unit 127 forces hydraulicfluid through the first hydraulic line 132, and into the first hydrauliccylinder 120, forcing the respective piston rod 124 to move thecounter-work-piece 128 in the direction of the arrow 146. Hydraulicfluid is thus forced through the hydraulic equalization lines 144, 145,optional hydraulic controller 147, and into the second hydrauliccylinder, forcing the respective piston rod 126 to simultaneously movethe work-piece 130 in the direction of the arrow 146. Magnetic forcesare offset as taught hereinabove. Reciprocal action is accomplished byreversing the flow of hydraulic fluid.

EXAMPLE I

An example of the invention illustrated in FIGS. 1-3 was modeledcomputationally based on the saturated magnetic properties of low carbonsteel and the gradient scale length of an existing 9 Teslasuperconducting magnet with a 5 inch diameter warm bore. The netextraction force was calculated for a pair of transmission shafts, oneacting as the work-piece and the other acting as the counter-work-piece.Multiple calculations were carried out with various spacing therebetweenin accordance with examples of the present invention and compared withthe extraction force on a single transmission shaft. Each theoreticalwork-piece had a volume of 60 cc, or 3.7 cubic inches. Results are shownin FIG. 11.

It is noted that in FIG. 11 the force on a pair of work pieces does notgo to zero when one work piece is at the center of the magnetic fieldwhere the field is uniform and force-free. That is because the counterwork piece is still close enough to the magnetic field to be subjectedto a non-negligible attractive force. Thus the net force on the pairremains finite when the work-piece is positioned at the center of themagnetic field. A solution to that residual force problem is shown inFIGS. 4-7 and corresponding description hereinabove, where thework-piece is moved farther away from the magnetic field, thus allowingforce-free processing of the work piece at the center of the magneticfield.

EXAMPLE II

An example of the invention illustrated in FIG. 8 was modeledcomputationally based on the saturated magnetic properties of low carbonsteel and the gradient scale length of an existing 9 Teslasuperconducting magnet with an 8 inch diameter warm bore. The netextraction force on a set of four uniformly spaced transmission shaftswas calculated for various spacing therebetween in accordance withexamples of the present invention and compared with the extraction forceon a single transmission shaft. For this case, each work-piece had avolume of 160 cc, or 9.8 cubic inches. Results are shown in FIG. 12.

The skilled artisan will recognize that the above examples illustratemerely few of the sundry possible configurations that can be employed incarrying out the present invention; many well-known mechanisms can beused alone or in combination. Examples of such mechanisms include, butare not limited to levers, pulleys, cables, winches, cranks, belts,gears, cogs, racks, pinions, chains, sprockets, cams, followers, shafts,sliding members, motors, engines, and various conventional devices forcontrolling the foregoing.

An important consideration in the carrying out of the present inventionis that the magnet coil design (for example, a Bitter resistive magnet,superconducting magnet, or a hybrid magnet) should be such that theopposing magnetic gradients are generally symmetric so that the finalforce will indeed be cancelled out in an optimal near-zero-forcecondition. In cases where the magnetic field is not symmetric, opposingwork-pieces can have corresponding asymmetry in order to cancel outopposing magnetic forces.

While there has been shown and described what are at present consideredto be examples of the invention, it will be obvious to those skilled inthe art that various changes and modifications can be prepared thereinwithout departing from the scope of the inventions defined by theappended claims.

What is claimed is:
 1. A carriage for high magnetic field environmentscomprising a plurality of work-piece separators disposed in an operablerelationship with a work-piece processing magnet having a magnetic fieldstrength of at least 1 Tesla for supporting and separating a pluralityof work-pieces by a preselected, essentially equal spacing, so that, asa first work-piece is inserted into said magnetic field, a secondwork-piece is simultaneously withdrawn from said magnetic field, so thatan attractive magnetic force imparted on the first work-piece offsets aresistive magnetic force imparted on the second work-piece.
 2. Acarriage in accordance with claim 1 further comprising a plurality ofwork-piece stations supported by said work-piece separators, saidwork-piece stations adapted for holding and releasing work-pieces.
 3. Acarriage for high magnetic field environments comprising a continuous,looped, flexible, work-piece holding conveyor disposed in an operablerelationship with a work-piece processing magnet having a magnetic fieldstrength of at least 1 Tesla, said conveyor defining a plurality ofessentially equally spaced work-piece holding positions so that, as saidconveyor moves a first work-piece into said magnetic field, saidconveyor also simultaneously withdraws a second work-piece from saidmagnetic field, so that an attractive magnetic force imparted on thefirst work-piece offsets a resistive magnetic force imparted on thesecond work-piece.
 4. A method of moving work-pieces into and out of ahigh magnetic field environment comprising the steps of: a. providing acontinuous, looped, flexible, work-piece holding conveyor disposed in anoperable relationship with a work-piece processing magnet having amagnetic field strength of at least 1 Tesla, said conveyor defining aplurality of essentially equally spaced work-piece holding positions;and b. moving said conveyor to withdraw a first work-piece from saidmagnetic field while simultaneously inserting a second work-piece intosaid magnetic field, so that an attractive magnetic force imparted onsaid second work-piece offsets a resistive magnetic force imparted onsaid first work-piece.
 5. A method in accordance with claim 4 furthercomprising an additional step of: c. moving said conveyor to insert athird work-piece into said magnetic field while simultaneouslywithdrawing said second work-piece from said magnetic field, so that anattractive magnetic force imparted on said third work-piece offsets aresistive magnetic force imparted on said second work-piece.